The present invention relates to a cylinder lock and a method for using same.
Cylinder locks conventionally include a housing having a cylindrical bore extending longitudinally therein. Within the bore is a plug which is mounted for rotation within the bore. The plug has a keyway for receiving a key and a row of plug holes therein having pins slidably movable within each of the holes. The housing also has a row of cylinder holes which are adapted to align with the plug holes within the plug. The cylinder holes include spring-mounted pins therein also.
When a key having the appropriate shape is inserted into the keyway, it aligns the pins in such a manner that the junctures between the pins correspond with the outer cylindrical surface of the plug. This permits the plug to rotate.
In many applications, it is necessary to be able to change the combinations of pins within the lock so that different shaped keys will work. Such an example may be found in apartment buildings where the owner desires to change the lock after a tenant has moved out of a particular apartment.
The present methods for changing these locks involve removing the lock entirely and inserting new sets of pins within the cylinder holes and plug holes s that the original key which opened the lock will no longer work, and so then a new key is required to open the lock.
Another problem encountered in many situations is the need for a service key which can be used to lock a particular door, but which will not open the lock once it is in its locked position. This particular type of lock has application where an employer desires to give an employee the ability to lock a door, but not the ability to open it.
Another feature which is desirable in many instances is the ability to give a person a key which will unlock the door once, but which will not unlock the door once it is locked a second time.
Therefore, a primary object of the present invention is the provision of an improved cylinder lock and method for using same.
A further object of the present invention is the provision of an improved cylinder lock which can have its pin combination changed without the need for removing the lock and manually repinning all of the channels or holes therein.
A further object of the present invention is the provision of a lock which can be set in a predetermined condition so that an access key will permit the door to be locked, but will not unlock the door.
A further object of the present invention is the provision of a cylinder lock which will accommodate an access key capable of opening the lock a single time, but which is incapable of unlocking the lock after it has been locked a second time.
A further object of the present invention is the provision of a device which is economical to manufacture, durable in use, and efficient in operation.